Quantity-of-light adjusting device and optical apparatus having the same

ABSTRACT

A quantity-of-light adjusting device includes a drive source, a base member having an opening formed therein, and a blade arranged to move by being driven by the drive source and having three openings formed therein side by side in a row in a moving direction of the blade, wherein, among the three openings formed in the blade, the opening situated in the middle of the row is larger than the opening formed in the base member.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of application Ser. No. 09/265,258,filed Mar. 9, 1999, now pending, which is a continuation in part ofapplication Ser. No. 09/166,631, filed Oct. 5, 1998, now abandoned.

BACKGROUND THE INVENTION

1. Field of the Invention

The present invention relates to a quantity-of-light adjusting devicefor use in a video camera, a digital still camera or the like.

2. Description of Relates Art

For motion-image taking cameras such as video cameras, there is used amotion-image quantity-of-light adjusting device which continuouslyvaries a diaphragm aperture from a full-aperture state up to afull-closed state. On the other hand, for still-image taking camerassuch as digital still cameras, there is used a still-imagequantity-of-light adjusting device which switches a diaphragm aperturebetween two positions, i.e., a full-aperture state and a small-aperturestate (e.g., F8) or which is capable of performing a shutter action inaddition to the quantity-of-light adjusting function.

Further, a quantity-of-light adjusting device which is capable ofadjusting a diaphragm aperture to at least three positions by means of aturret diaphragm mechanism is disclosed in, for example, JapaneseLaid-Open Utility Model Application No. HEI 3-52725. In thisquantity-of-light adjusting device, a mechanical diaphragm mechanism isused to mechanically restrict a diaphragm member to the full-apertureposition by means of a torsion spring and this position is changed overto another position by transmitting a driving force of a driving part tothe diaphragm member through gears.

BRIEF SUMMERY OF THE INVENTION

In accordance with one aspect of the invention, there is provided aquantity-of-light adjusting device, which comprises a drive source, abase member having an opening formed therein, and a blade arranged tomove by being driven by the drive source and having three openingsformed therein side by side in a row in a moving direction of the blade,wherein, among the three openings formed in the blade, the openingsituated in the middle of the row is larger than the opening formed inthe base member.

In accordance with another aspect of the invention, there is provided aquantity-of-light adjusting device, which comprises a drive source, abase member having an opening formed therein, and a blade arranged tomove by being driven by the drive source and having two openings formedtherein side by side in a row in a moving direction of the blade,wherein, between the two openings formed in the blade, there is provideda light blocking area which is larger than the opening formed in thebase member.

These and other aspects and features of the invention will becomeapparent from the following detailed description of preferredembodiments thereof taken in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

FIG. 1 is an exploded perspective view showing the mechanicalarrangement of a quantity-of-light adjusting device according to a firstembodiment of the invention.

FIGS. 2(A) to 2(D) are diagrams for explaining the action of a steppingmotor included in the quantity-of-light adjusting device according tothe first embodiment.

FIG. 3 is a schematic diagram showing the arrangement of a digitalcamera equipped with the quantity-of-light adjusting device according tothe first embodiment.

FIG. 4 is a flow chart showing a control operation of the digital camerashown in FIG. 3.

FIGS. 5(A) to 5(C) are plan views showing the mechanical arrangement ofa quantity-of-light adjusting device according to a second embodiment ofthe invention.

FIGS. 6(A) to 6(D) are diagrams for explaining the action of a steppingmotor included in the quantity-of-light adjusting device according tothe second embodiment.

FIG. 7 is a flow chart showing a control operation of a camera equippedwith the quantity-of-light adjusting device according to the secondembodiment.

FIGS. 8(A) to 8(C) are diagrams for explaining the action of aquantity-of-light adjusting device according to a third embodiment ofthe invention.

FIG. 9 is a flow chart showing an operation of a camera (having a CCD ofthe all-pixels read-out type) equipped with the quantity-of-lightadjusting device according to the third embodiment.

FIG. 10 is a flow chart showing an operation of a camera-(having a CCDof the sequential read-out type) equipped with the quantity-of-lightadjusting device according to the third embodiment.

FIG. 11 is a schematic diagram showing the arrangement of a part of aquantity-of-light adjusting device according to a fourth embodiment ofthe invention.

FIGS. 12(A), 12(B) and 12(C) are diagrams for explaining operations ofdiaphragm blades of the quantity-of-light adjusting device shown in FIG.11 during a still-image pickup mode.

FIG. 13 is a flow chart showing the operation of a camera equipped withthe quantity-of-light adjusting device shown in FIG. 11.

FIG. 14 is a diagram for explaining an operation of the diaphragm bladesof the quantity-of-light adjusting device shown in FIG. 11 during amotion-image pickup mode.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, preferred embodiments of the invention will be described indetail with reference to the drawings.

(First Embodiment)

FIG. 1 shows the mechanical arrangement of a quantity-of-light adjustingdevice according to a first embodiment of the invention. Referring toFIG. 1, a stepping motor 1 is employed as a drive source. An arm member2 is arranged to rotate integrally with the output shaft of the steppingmotor 1. A diaphragm case 3 is provided with a fixed-aperture opening 3c, which defines an optical full-aperture diameter.

A diaphragm blade 4 is made of a sheet material measuring about 0.1 mmin thickness. The diaphragm blade 4 has a shaft hole 4 b, which isrotatably fit on a shaft part 3 b provided on the diaphragm case 3. Onone side of the diaphragm blade 4 across the shaft hole 4 b, there isprovided a driving slot 4 a, into which a pin 2 a formed on the armmember 2 is inserted. On the other side of the diaphragm blade 4 acrossthe shaft hole 4 b, there are provided an aperture hole 4 c, which islarger in diameter than the fixed-aperture opening 3 c, and a firstsmall-aperture hole 4 d and a second small-aperture hole 4 e, each ofwhich is smaller in diameter than the fixed-aperture opening 3 c.

An ND filter 5 is bonded to the diaphragm blade 4 to cover the secondsmall-aperture hole 4 e. A blade retainer 6 is secured to the diaphragmcase 3, which accommodates the diaphragm blade 4, to prevent thediaphragm blade 4 from coming off from the inside of the diaphragm case3.

The stepping motor 1 is secured with screws 7 to the outer surface ofthe diaphragm case 3. The arm member 2 protrudes into the inside of thediaphragm case 3 through a sectorial window part 3 a provided in thediaphragm case 3. The pin 2 a provided on the fore end of the arm member2 fits in the driving slot 4 a formed in the diaphragm blade 4. When thestepping motor 1 is actuated, therefore, the diaphragm blade 4 is causedto swing on the shaft part 3 b upward or downward as viewed in FIG. 1.Accordingly, the diaphragm blade 4 is changed over among a full-apertureposition in which the aperture hole 4 c coincides, in position in theoptical axis direction, with the fixed-aperture opening 3 c of thediaphragm case 3, a small-aperture position in which the firstsmall-aperture hole 4 d coincides, in position in the optical axisdirection, with the fixed-aperture opening 3 c, and a filter position inwhich the second small-aperture hole 4 e (the ND filter 5) coincides, inposition in the optical axis direction, with the fixed aperture hole 3c.

The diaphragm blade 4 is driven into each of the above-stated positionsin the following manner. Referring to FIGS. 2(A) to 2(D), the steppingmotor 1 is composed of a rotor magnet 1 a which is formed integrallywith the output shaft and a stator ring 1 b which encompasses the rotormagnet 1 a. The stepping motor 1 has eight magnetic stop positions inone round of rotation. In the case of the first embodiment, the steppingmotor 1 is driven within the range of three magnetic stop positionswhich are adjacent to each other among these eight magnetic stoppositions.

When the stepping motor 1 comes to a stop at the middle magnetic stopposition among the three magnetic stop positions, as shown in FIG. 2(B),that is, when a high level signal is inputted only to an input terminalA among the input terminals A, −A, B and −B, as shown in FIG. 2(D), thediaphragm blade 4 is set at the full-aperture position P1.

However, the magnetic stop position of the stepping motor 1 fluctuatesto a certain degree. Hence, if the diameter (size) of the aperture hole4 c is assumed to be the same as that of the fixed-aperture opening 3 c,the aperture hole 4 c and the fixed-aperture opening 3 c tend to deviatefrom each other due to fluctuations of the magnetic stop position,resulting in the full-aperture diameter varying. To solve this problem,in the first embodiment, the aperture hole 4 c is formed in an ellipticshape extending at least in the direction of driving in such a way as toabsorb the fluctuations of the magnetic stop position, so that thefull-aperture diameter can be always kept constant. In other words, thefull-aperture diameter is determined by the fixed aperture hole 3 c ofthe diaphragm case 3.

Further, stopper faces 3 e and 3 d are formed at the upper and lower endparts of the sectorial window part 3 a of the diaphragm case 3. Thesestopper faces 3 e and 3 d are respectively located more inward than thetwo side magnetic stop positions among the three magnetic stoppositions.

Therefore, when a high level signal is inputted only to the inputterminal −B of the stepping motor 1, as shown in FIG. 2(D), the armmember 2 is caused to abut on the stopper face 3 d by a magnetic forcewhich urges the rotor magnet la to rotate toward a lower magnetic stopposition, so that the diaphragm blade 4 can be accurately brought to thesmall-aperture position P2, as shown in FIG. 2(A).

When a high level signal is inputted only to the input terminal B of thestepping motor 1 as shown in FIG. 2(D), the arm member 2 is caused toabut on the stopper face 3 e by a magnetic force which urges the rotormagnet 1 a to rotate toward an upper magnetic stop position, so that thediaphragm blade 4 can be accurately brought to the filter position P3,as shown in FIG. 2(C).

The arm member 2 and the diaphragm blade 4 are thus pushed against thestopper faces 3 d or 3 e by the magnetic force of the stepping motor 1to set the diaphragm blade 4 at the small-aperture position P2 or at thefilter position P3. By virtue of this arrangement, the centers of thesmall-aperture holes 4 d and 4 e which correspond to the two positionsP2 and P3, respectively, can be accurately set without deviating fromthe optical axis (the center of the fixed-aperture opening 3 c) of thequantity-of-light adjusting device.

After the diaphragm blade 4 is moved to any of the above-stated threepositions P1, P2 and P3, the diaphragm blade 4 can be kept in thatposition by the cogging torque of the rotor magnet la even after thehigh level signal inputted to the input terminal A, −A, B or −B is cutoff.

FIG. 3 shows the arrangement of a digital still camera equipped with theabove-stated quantity-of-light adjusting device. In FIG. 3, referencenumerals 10 and 12 denote fixed lens groups. Reference numeral 11denotes a moving lens group provided for varying magnification.Reference numeral 13 denotes a moving lens group provided for focusing.These lens groups constitute an ordinary rear-focus-type lens having apositive-negative-positive-positive refractive power arrangement.

The digital still camera shown in FIG. 3 further includes thequantity-of-light adjusting device 14, an image sensor 15 composed of aCCD, etc., a shutter switch 17, a microcomputer 18, and a memory 18.

An operation of the microcomputer 16 is next described with reference toFIG. 4 which is a flow chart. When a power supply is turned on by thephotographer, the flow of operation begins at a step S1. At the step S1,the shutter switch 17 is pushed halfway, i.e., to the extent of thefirst stroke. At a step S2, the microcomputer 16 drives thequantity-of-light adjusting device 14 to the full-aperture position. Ata step S3, a light measuring action is performed through the imagesensor 15 to obtain information on the measured light. At a step S4, adecision is made for a position which is most apposite to photo-takingamong the three positions. At a step S5, S6 or S7, the quantity-of-lightadjusting device 14 is driven to the position decided.

At a step S8, a check is made to find if the second stroke (fullpushing) operation is performed on the shutter switch 17 by thephotographer. If so, the flow of operation proceeds to a step S9. At thestep S9, the microcomputer 16 clears image data of the image sensor 15for once. At a step S10, the microcomputer 16 makes adjustment for anoptimum exposure in accordance with the gain of a camera circuit, thespeed of a digital shutter, etc. At a step S11, image data isaccumulated and taken in until the lapse of the optimum exposure time.At a step S12, the image data thus taken in is recorded in the memory18.

As described above, in the case of the digital still camera which hasthe CCD 15 arranged to have the electric charge of signals accumulatedat a photosensitive part and transferred to a storage part to preventfogging of light, no mechanical shutter action is necessary.

(Second Embodiment)

In the case of the first embodiment, the invention is applied to acamera of the kind using an image sensor (CCD). The CCD which isemployed as the image sensor has two types. In one type, the CCD has astorage part to which the signal electric charge accumulated at aphotosensitive part is transferred. In the other type, the CCD has nosuch storage part. In the first embodiment, the quantity-of-lightadjusting device is used in the camera wherein the CCD is of the formertype which obviates the necessity of any mechanical shutter (for afull-closed state). In the case of a second embodiment of the invention,the quantity-of-light adjusting device is used for a camera having a CCDof the latter type which necessitates the use of a mechanical shutter.

FIGS. 5(A) to 5(C) show the arrangement of the quantity-of-lightadjusting device according to the second embodiment. Referring to FIGS.5(A) to 5(C), a stepping motor 21 is employed as a drive source. An armmember 22 is arranged to rotate integrally with the output shaft of thestepping motor 21. A diaphragm case 23 is provided with an opening 23 d.

A diaphragm blade 24 is made of a sheet material measuring about 0.1 mmin thickness. The diaphragm blade 24 has guide slots 24 b and 24 carranged to be fit on guide pins 23 b and 23 c provided on the diaphragmcase 23. On the upper side of the guide slot 24 b in the diaphragm blade24, there is formed a driving slot 24 a. On one side of the guide slots24 b and 24 c, there are formed a large-diameter aperture hole 24 d anda small-diameter aperture hole 24 e. Further, a light blocking part 24 fis provided between the large-diameter aperture hole 24 d and thesmall-diameter aperture hole 24 e.

The stepping motor 21 is secured to the outer surface of the diaphragmcase 23. The arm member 22 protrudes into the inside of the diaphragmcase 23 through a square window part 23 a formed in the diaphragm case23. A pin 22 a provided at the fore end of the arm member 22 fits in thedriving slot 24 a of the diaphragm blade 24. Therefore, when thestepping motor 21 is actuated, the diaphragm blade 24 moves upward ordownward, as viewed in FIG. 5(A), while being guided by the guide pins23 b and 23 c. Accordingly, the diaphragm blade 24 provides asmall-aperture position P2 in which the small-diameter aperture hole 24e coincides, in position in the optical axis direction, with the opening23 d of the diaphragm case 23, as shown in FIG. 5(A), a full-closed(fully light-blocked) position P1 in which the light blocking part 24 fcoincides, in position in the optical axis direction, with the opening23 d, as shown in FIG. 5(B), and a full-aperture position P3 in whichthe large-diameter aperture hole 24 d coincides, in position in theoptical axis direction, with the opening 23 d, as shown in FIG. 5(C).Further, the opening 23 d of the diaphragm case 23 has a larger diameterthan the large-diameter aperture hole 24 d. Therefore, the full-aperturediameter of the quantity-of-light adjusting device is defined by thelarge-diameter aperture hole 24 d and not by the opening 23 d formed inthe diaphragm case 23.

The diaphragm blade 24 is driven into each of the above-sated positionsin the following manner. Referring to FIGS. 6(A) to 6(D), the steppingmotor 21 is composed of a rotor magnet 21 a which is formed integrallywith the output shaft and a stator ring 21 b which encompasses the rotormagnet 21 a. The stepping motor 21 has eight magnetic stop positions inone round of rotation. In the case of the second embodiment, thestepping motor 21 is driven within the range of three magnetic stoppositions which are adjacent to each other among these eight magneticstop positions.

When the stepping motor 21 comes to a stop at the middle magnetic stopposition among the three magnetic stop positions, as shown in FIG. 6(B),that is, when a high level signal is inputted only to an input terminalA among the input terminals A, −A, B and −B, as shown in FIG. 6(D), thediaphragm blade 24 is set at the full-closed position P1. This enablesthe quantity-of-light adjusting device to function as a mechanicalshutter.

Further, stopper faces 23 f and 23 e are formed at the upper and lowerend parts of the sectorial window part 23 a of the diaphragm case 23.These stopper faces 23 e and 23 f are located more inward than theupper-end and lower-end magnetic stop positions among the three magneticstop positions.

Therefore, when a high level signal is inputted only to the inputterminal −B of the stepping motor 21, as shown in FIG. 6(D), the armmember 22 is caused to about on the stopper face 23 f by a magneticforce which urges the rotor magnet 21 a to rotate toward the uppermagnetic stop position in a state of being pushed against the stopperface 23 f, so that the diaphragm blade 24 can be accurately brought tothe full-aperture position P3, as shown in FIG. 6(A).

When a high level signal is inputted only to the input terminal B of thestepping motor 21 as shown in FIG. 6(D), the arm member 22 is caused toabut on the stopper face 23 e by a magnetic force which urges the rotormagnet 21 a to rotate toward the lower magnetic stop position in a stateof being pushed against the stopper face 23 e, so that the diaphragmblade 24 can be accurately brought to the small-aperture position P2, asshown in FIG. 6(C).

The arm member 22 is thus pushed against the stopper faces 23 e or 23 fby the magnetic force of the stepping motor 21 to set the diaphragmblade 24 at the small-aperture position P2 or at the full-apertureposition P3 without any deviation. Therefore, the centers of theaperture holes 24 e and 24 d which are provided in the diaphragm blade24 to correspond to the two positions P2 and P3 can be accurately set inposition without deviating from the optical axis (the center of theopening 23 d) of the quantity-of-light adjusting device.

After the diaphragm blade 24 is moved to any of the above-stated threepositions P1, P2 and P3, the diaphragm blade 24 can be kept in thatposition by the cogging torque of the rotor magnet 21 even after thehigh level signal inputted to the input terminal A, −A, B or −B is cutoff.

The quantity-of-light adjusting device according to the secondembodiment is used for a camera which differs only in type of the imagesensor from the camera of the first embodiment. In other words, in thesecond embodiment, the microcomputer 16 controls the quantity-of-lightadjusting device, etc., according to an operation performed on theshutter switch 17.

An operation of the microcomputer 16 is next described with reference toFIG. 7 which is a flow chart. When the power supply is turned on by thephotographer, the flow of operation begins at a step S31. At the stepS31, the microcomputer 16 drives the quantity-of-light adjusting device14 to the full-closed position, thereby bringing the shutter into aclosed state. At a step S32, the shutter switch 17 is pushed halfway,i.e., to the extent of the first stroke. At a step S33, themicrocomputer 16 drives the quantity-of-light adjusting device 14 to thefull-aperture position. At a step S34, a light measuring action isperformed through the image sensor 15 to obtain information on themeasured light. At a step S35, a decision is made for a position whichis most apposite to photo-taking among the two positions (thefull-aperture position and the small-aperture position). At a step S36or S37, the quantity-of-light adjusting device 14 is driven to theposition decided, thereby bringing the shutter into an open state.

At a step S38, a check is made to find if the second stroke (fullpushing) operation on the shutter switch 17 is performed by thephotographer. If so, the flow of operation proceeds to a step S39. Atthe step S39, the microcomputer 16 clears image data of the image sensor15 for once. At a step S40, the microcomputer 16 makes adjustment for anoptimum exposure in accordance with the gain of a camera circuit, thespeed of a digital shutter, etc. At a step S41, after the lapse of timeof the optimum exposure, the quantity-of-light adjusting device 14 isbrought back to the full-closed position, thereby bringing the shutterto the closed state. At a step S42, with a double exposure beingprevented, image data which has been accumulated is taken in. At a stepS43, the image data is recorded in the memory 18.

The invention is not limited to the shapes and driving directions of thediaphragm member described in the embodiments. The invention isapplicable also to a quantity-of-light adjusting device of such a typehaving two or four positions (for example, a full-closed position, afull-aperture position, a large-aperture position and a small-apertureposition).

Further, the invention is applicable not only to a digital still camerabut also to optical apparatuses of various kinds, such as a videocamera, etc.

(Third Embodiment)

FIGS. 8(A) to 8(C) show the arrangement of a quantity-of-light adjustingdevice according to a third embodiment of the invention. Thequantity-of-light adjusting device includes a first diaphragm blade 101and a second diaphragm blade 102. The first and second diaphragm blades101 and 102 respectively have slots 101-c and 102-c which are fit onshaft parts 106 a and 106 b formed at end parts of a driving arm 106which is arranged to swing on a swing shaft O. Further, the first andsecond diaphragm blades 101 and 102 respectively have guide slots 101-dand 102-b which are fit on guide pins 104 and 105 formed on a base plate200. When the driving arm 106 is driven to swing on the swing shaft O byan actuator 100 such as a motor or the like, the first and seconddiaphragm blades 101 and 102 are caused to move upward or downward, asviewed in FIG. 8(A), while being guided by the guide pins 104 and 105.

Further, the first and second diaphragm blades 101 and 102 arerespectively provided with continuously-variable aperture parts 101-band 102-b for enabling continuous aperture adjustment between afull-aperture position and a full-closed position, and fixed-apertureparts 101-a and 102-a for obtaining specific aperture diameters.Reference numeral 103 denotes an opening formed in the base plate 200.The opening 103 determines the full-aperture diameter of thequantity-of-light adjusting device.

The quantity-of-light adjusting device which is arranged as describedabove operates as follows. When the driving arm 106 swings to an angleposition A which is one end of its swinging range, as shown in FIG.8(A), the two diaphragm blades 101 and 102 are brought to the full-openpositions to bring about a state in which a light flux passing throughthe opening 103 is completely unblocked by the continuously-variableaperture parts 101-b and 102-b.

When the driving arm 106 swings to an angle position B, as shown in FIG.8(B), the two diaphragm blades 101 and 102 are brought to thefull-closed positions to bring about a state in which a light fluxpassing through the opening 103 is completely blocked by thecontinuously-variable aperture parts 101-b and 102-b.

Further, when the driving arm 106 swings to an angle position C which isthe other end of the swinging range, as shown in FIG. 8(C), thefixed-aperture parts 101-a and 102-a of the diaphragm blades 101 and 102come to coincide with each other on the opening 103, thereby giving aspecific aperture diameter.

In the third embodiment, when the driving arm 106 is driven tocontinuously move between the angle positions A and B, the aperturediameter defined by the continuously-variable aperture parts 101-b and102-b of the two diaphragm blades 101 and 102 can be continuouslychanged.

Further, when the position of the driving arm 106 is switched betweenthe two positions, i.e., the angle position A and the angle position C,the full aperture formed by the continuously-variable aperture parts101-b and 102-b of the diaphragm blades 101 and 102 and the fixedaperture formed by the fixed-aperture parts 101-a and 102-a can bechanged from one over to the other.

Therefore, in a case where the quantity-of-light adjusting device ismounted on a camera which is capable of taking both motion images andstill images, the quantity of light incident on the image sensor, etc.,can be adjusted by continuously driving the driving arm 106 between theangle positions A and B (a motion-image diaphragm mode) when the camerais in a motion-image taking mode, and by switching the position of thedriving arm 106 between the angle positions A and C (a still-imagediaphragm mode) when the camera is in a still-image taking mode.

With the two position switch-over control over the driving arm 106arranged to drive the driving arm 106 from the angle position A or C tothe angle position B (a still-image shutter mode), the full-aperturestate or the specific-aperture state can be changed at once over to thefull-closed state as a shutter action. Therefore, the quantity-of-lightadjusting device can be used as a shutter in the still-image takingmode.

An operation of a camera which is capable of taking both motion imagesand still images and is equipped with the quantity-of-light adjustingdevice according to the third embodiment is next described withreference to FIG. 9 which is a flow chart. The camera is provided with aCCD of the all-pixels read-out type. The flow chart of FIG. 9 then showsthe operation both in the motion-image diaphragm mode and thestill-image diaphragm mode (the two-position switch-over operation).

As a step S101, information about which of the motion-image taking modeor the still-image taking mode is selected for shooting to be made fromnow is taken in. At a step S102, a discrimination is made between themotion-image taking mode, i.e., the motion-image diaphragm mode, and thestill-image taking mode, i.e., the still-image diaphragm mode. In thecase of the motion-image diaphragm mode, the flow of operation proceedsto a step S103. At the step S103, the quantity-of-light adjusting deviceis caused to continuously adjust the quantity of light on the basis ofinformation on the luminance from the CCD (image sensor). At a stepS104, a motion-image taking operation is performed.

On the other hand, in the case of the still-image diaphragm mode, theflow proceeds to a step S105. At the step S105, a shutter button isdetected to have been pushed halfway of the full stroke of operation. Atthe next step S106, the storage time of the CCD and an aperture valueare decided on the basis of information on the luminance from the CCD.The aperture of the quantity-of-light adjusting device is thusautomatically adjusted. At a step S107, the shutter button is found tohave been pushed to the full stroke. At a step S108, after the lapse ofthe decided storage time of the CCD, the pixel information of the CCD isread out. At a step S109, the still-image taking operation is brought toan end.

FIG. 10 is a flow chart showing an operation of the camera performed ina case where a CCD of the sequential read-out type is employed for thecamera. The operation is performed in the motion-image diaphragm modeand the still-image diaphragm/shutter mode (shutter operation).

At a step S101′ of FIG. 10, information about which of the motion-imagetaking mode or the still-image taking mode is selected for shooting tobe made from now is taken in. At a step S102′, a discrimination is madebetween the motion-image taking mode, i.e., the motion-image diaphragmmode, and the still-image taking mode, i.e., the still-imagediaphragm/shutter mode. In the case of the motion-image diaphragm mode,the flow of operation proceeds to a step S103′. At the step S103′, thequantity-of-light adjusting device is caused to continuously adjust thequantity of light on the basis of information on the luminance from theCCD (image sensor). At a step S104′, a motion-image taking operation isperformed.

On the other hand, in the case of the still-image diaphragm/shuttermode, the flow proceeds to a step S105′. At the step S105′, a shutterbutton is detected to have been pushed halfway of the full stroke ofoperation. At the next step S106′, the storage time of the CCD and anaperture value are decided on the basis of information from theluminance of the CCD. The aperture of the quantity-of-light adjustingdevice is thus automatically adjusted. At a step S107′, the shutterbutton is found to have been pushed to the full stroke. At a step S108′,after the lapse of the decided storage time of the CCD, the aperture ofthe quantity-of-light adjusting device is closed and the pixelinformation of the CCD is read out. At a step S109′, the still-imagetaking operation is brought to an end.

(Fourth Embodiment)

FIG. 11 and FIGS. 12(A) to 12(C) schematically show the arrangement of aquantity-of-light adjusting device according to a fourth embodiment ofthe invention. Referring to FIG. 11 and FIGS. 12(A) to 12(C), thequantity-of-light adjusting device according to the fourth embodimentincludes a stepping motor 201, a lever 202 arranged to transmit adriving force from the stepping motor 201, a frame provided for limitinga driving range of the lever 202, an upper diaphragm blade 204 and alower diaphragm blade 205 which are driven by the stepping motor 201 viathe lever 202, and a diaphragm base plate 207 having formed therein anaperture opening 206 through which a light flux passes.

In the quantity-of-light adjusting device according to the fourthembodiment, when the stepping motor 201 is changed from a non-energizedstate to an energized state, the stepping motor 201 is driven to aninitial operation position (predetermined operation position), whichcauses the lever 202 to be stopped at a middle position within the frame203. In this instance, both the diaphragm blades 204 and 205 are drivento a closed position (reference position), in which the aperture opening206 formed in the diaphragm base plate 207 is fully covered by thediaphragm blades 204 and 205.

When the energized state of the stepping motor 201 is changed over so asto drive, for one step in the clockwise direction as viewed in FIG. 11,the stepping motor 201 which has been stopped at the initial operationposition, the stepping motor 201 rotates until the lever 202 abuts onone end 203 a of the frame 203. According to the rotation of thestepping motor 201, both the diaphragm blades 204 and 205 are drivenfrom the closed position to a small-aperture position, in which theaperture opening 206 is partly covered to realize a small-diameteraperture through which a light flux passes.

Also, when the energized state of the stepping motor 201 is changed overso as to drive, for one step in the counterclockwise direction as viewedin FIG. 11, the stepping motor 201 which has been stopped at the initialoperation position, the stepping motor 201 rotates until the lever 202abuts on the other end 203 b of the frame 203. According to the rotationof the stepping motor 201, both the diaphragm blades 204 and 205 aredriven from the closed position to an open position (fully-openedaperture position), in which the aperture opening 206 is not covered atall, to realize a full aperture.

In the quantity-of-light adjusting device arranged as described above,the stepping motor 201 is controlled by a microcomputer incorporated ina camera. In the following, a control operation of the microcomputer forthe camera including the quantity-of-light adjusting device will bedescribed by reference to the flow chart of FIG. 13.

When a power supply of the camera is turned on, the camera microcomputergives an instruction to a motor control circuit (not shown) to changethe stepping motor 201 from the non-energized state to the energizedstate. Accordingly, the stepping motor 201 is driven to the aboveinitial operation position, so that both the diaphragm blades 204 and205 are driven to the closed position (step 701). By this operation, theso-called resetting operation of the quantity-of-light adjusting deviceis completed. Therefore, it is possible to dispense with an automaticclosing spring or member, a sensor for detecting the initial position ofa diaphragm blade, or the like, which would be required in theconventional quantity-of-light adjusting device.

Subsequently, the microcomputer makes a check to find whether theoperation mode of the camera is set to a still-image pickup mode or to amotion-image pickup mode (step 702). If the operation mode of the camerais set to the still-image pickup mode, the flow of operation stands bywith both the diaphragm blades 204 and 205 stopped at the closedposition (step 703).

Then, when a release switch of the camera is pushed (turned on) (step704), the camera microcomputer causes a light measuring device (notshown) to measure the luminance of a picked-up image plane (step 705).Upon receipt of the luminance information from the light measuringdevice, the camera microcomputer makes a check to find if the luminanceinformation indicates a value less than a predetermined reference value(step 706).

If it is found that the luminance information indicates a value lessthan the predetermined reference value, in order to obtain an appositeexposure value, the microcomputer causes the motor control circuit todrive the stepping motor 201 for one step in the counterclockwisedirection as viewed in FIG. 11, so that the diaphragm blades 204 and 205are driven to the open position. After that, a shutter operation isperformed at an apposite shutter speed to expose an image sensor such asa CCD to light, thereby completing the still-image pickup operation(step 707).

On the other hand, if it is found that the luminance informationindicates a value not less than the predetermined reference value, inorder to obtain an apposite exposure value, the microcomputer causes themotor control circuit to drive the stepping motor 201 for one step inthe clockwise direction as viewed in FIG. 11, so that the diaphragmblades 204 and 205 are driven to the small-aperture position. Afterthat, the shutter operation is performed at an apposite shutter speed,thereby completing the still-image pickup operation (step 708).

Further, if the operation mode of the camera is set to the motion-imagepickup mode, a control method of the motor control circuit for thequantity-of-light adjusting device is changed from a control methodadapted for the still-image pickup mode to a control method adapted forthe motion-image pickup mode (step 709). At the same time, the cameramicrocomputer causes the light measuring circuit to measure theluminance of a picked-up image plane (step 710). Then, in order toobtain an apposite exposure value, the microcomputer calculates adriving direction and a driving step number of the stepping motor 201according to a change of the luminance information, and changes over theenergized state of the stepping motor 201 through the motor controlcircuit. By this operation, the diaphragm blades 204 and 205 arecontrolled in such a way as to form an apposite aperture openingdiameter between the open position and the closed position, as shown inFIG. 14, so that the motion-image pickup operation is performed by theimage sensor such as a CCD (step 711).

When the still-image or motion-image pickup operation is completed inthe above-stated manner and the power supply of the camera is turnedoff, the microcomputer changes over the energized state of the steppingmotor 201 through the motor control circuit to temporarily return thestepping motor 201 to the initial operation position (i.e., to drive thediaphragm blades 204 and 205 to the closed position), and, after that,stops energizing the stepping motor 201 (step 712). Accordingly, it ispossible to surely return the diaphragm blades 204 and 205 to the closedposition and surely retain them at that position by means of a coggingtorque of the stepping motor 201 itself, without necessitating anyautomatic closing spring or member which would be required in theconventional quantity-of-light adjusting device.

Further, in the fourth embodiment, a description is made of aquantity-of-light adjusting device which is adapted for both thestill-image pickup operation and the motion-image pickup operation.However, the invention is applicable to a quantity-of-light adjustingdevice which is adapted for only one of the still-image pickup operationand the motion-image pickup operation.

Further, the initial position of the stepping motor 201 does not have tobe a position corresponding to the closed position of the diaphragmblades 204 and 205, differently from the fourth embodiment.

What is claimed is:
 1. A quantity-of-light adjusting device comprising:a) a drive source; b) a base member having an opening formed therein;and c) a blade which is driven by said drive source and which has acutout part continuously varying a quantity of light passing through theopening formed in base member and a hole for providing a specificaperture value to said opening formed in said base member.
 2. Aquantity-of-light adjusting device according to claim 1, wherein saidcutout part does not block a light flux passing through the openingformed in said base member when said blade moves to one end of a movingrange thereof, and the hole for providing the specific aperture valuecoincides in position with the opening formed in said base member whensaid blade moves to another end of the moving range thereof.
 3. Aquantity-of-light adjusting device according to claim 1, wherein aclosed position in which said blade blocks a light flux passing throughthe opening formed in said base member is set between one end andanother end of a moving range within which said blade is driven.
 4. Aquantity-of-light adjusting device according to claim 3, wherein saiddrive source performs continuous driving when said blade moves betweenone end of the moving range and the closed position, and said drivesource performs switching driving between two positions when said blademoves between another end of the moving range and the closed position.5. An optical apparatus having a quantity-of-light adjusting device,comprising: a) a drive source; b) a base member having an opening formedtherein; and c) blade which is driven by said drive source and which hasa cutout part for continuously varying a quantity of light passingthrough the opening formed in said base member and a hole for providinga specific aperture value to said opening formed in said base member. 6.An optical apparatus according to claim 5, wherein said cutout part doesnot block a light flux passing through the opening formed in said basemember when said blade moves to one end of a moving range thereof, andthe hole for providing the specific aperture value coincides in positionwith the opening formed in said base member when said blade moves toanother end of the moving range thereof.
 7. An optical apparatusaccording to claim 5, wherein a closed position in which said bladeblocks a light flux passing through the opening formed in said basemember is set between one end and another end of a moving range withinwhich said blade is driven.
 8. An optical apparatus according to claim7, wherein said drive source performs continuous driving when said blademoves between one end of the moving range and the closed position, andsaid drive source performs switching driving between two positions whensaid blade moves between another end of the moving range and the closedposition.
 9. A quantity-of-light adjusting device comprising: a) astepping motor arranged to be driven to an initial position when it isin a predetermined energized state; b) a base member having an openingformed therein; c) a plurality of blades arranged to be driven by saidstepping motor, said plurality of blades varying a quantity of lightpassing through the opening formed in said base member.
 10. Aquantity-of-light adjusting device according to claim 9, wherein, whensaid stepping motor is driven to the initial position, said plurality ofblades moves to such a closing position as to close the opening.
 11. Aquantity-of-light adjusting device according to claim 9, wherein saidplurality of blades have a first cutout part and a second cutout partthat is smaller than the first cutout, and said plurality of blades aremoved by said stepping motor, and thereby they form a first state wheresaid first cutout part continuously varies from an opening state to aclosing state to said opening in said base member, and they form asecond state where the second cutout part provides a specific aperturevalue to said opening in said base member.
 12. A quantity-of-lightadjusting deice according to claim 10, wherein, after a power supply istuned off, said stepping motor retains said plurality of blades at theclosing position by a cogging torque of said stepping motor.
 13. Anoptical apparatus having a quantity-of-light adjusting device,comprising: a) a stepping motor arranged to be driven to an initialposition when it is in a predetermined energized state; b) a base memberhaving an opening formed therein; c) a plurality of blades arranged tobe driven by said stepping motor, said plurality of blades varying aquantity of light passing through the opening formed in said basemember.
 14. An optical apparatus according to claim 13, wherein, whensaid stepping motor is driven to the initial position, said plurality ofblades moves to such a closing position as to dose the opening.
 15. Anoptical apparatus according to claim 13, wherein said plurality ofblades have a first cutout part and a second cutout part that is smallerthan the first cutout, and said plurality of blades are moved by saidstepping motor, and thereby they form a first state where said firstcutout part continuously varies from an opening state to a closing stateto said opening in said base member, and they form a second state wherethe second cutout part provides a specific aperture value to saidopening in said base member.
 16. An optical apparatus according to claim14, wherein, when the option of optical apparatus stops, a power supplyis turned off after said stepping motor is driven to said initialposition, and said stepping motor retains said plurality of blades atthe closing position by a cogging torque of said stepping motor.